全新java初学者实践教程6(Java SE5.0版)
+0Gep}&z. 基本语法3
kP$gl| 37xxVbik kg@h R} 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
d]EvC> .TC
`\mV [font="Times] 1.循环语句[font="Times]:while,do-while,for
sd53 _sV 3;NRW+ [font="Times]2.分支语句[font="Times]:if-else,switch,
7VcVI? ? [font="Times]
n^N]iw{G 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
M-N2>i# [font="Times]
ozLJ#eOE9 4.异常处理语句[font="Times]:try-catch-finally,throw
fP58$pwu (, "E9. 实践:
$8k_M [font="Times] 1.循环语句
keskD [font="Times] while 语句
NrcCUZ .:N [font="Times]class While {
LltguNM$ [font="Times]public static void main(String args[]) {
pm\X*t}L [font="Times]int n = 10;
}eM<A$J [font="Times]while(n > 0) {
BA,6f?ktXS [font="Times]System.out.println("tick " + n);
s.' \&B[ [font="Times]n--;
p;$9W+H0 [font="Times]}
: !3 y>bP) [font="Times]}
Nl`ry2"< [font="Times]}
C4]%pi [font="Times] do…while 语句
2<Bv=B [font="Times] class DoWhile {
@88i/ Z_ [font="Times]public static void main(String args[]) {
Ky#B'Bh}`g [font="Times]int n = 10;
t[hocl/6 [font="Times]do {
on?/tHys [font="Times]System.out.println("tick " + n);
+E|ouFI [font="Times]n--;
9^ p{/Io [font="Times]} while(n > 0);
|+-i'N9 [font="Times]}
RWCS
u$ [font="Times]}
&pjV4m|j< 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
~aAJn IO [font="Times] for语句
Y,btL'[W [font="Times] class ForTick {
f<Tz#w&6W [font="Times]public static void main(String args[]) {
W"(`n4hi3 [font="Times]int n;
pm~;:#z7
[font="Times]for(n=10; n>0; n--)
N+qLxk [font="Times]System.out.println("tick " + n);
"H<#91^| [font="Times]}
NxO^VUD [font="Times]}
<0)ud)~u 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
Ch"8cl;Fm 还有啊,[font="Times]for循环的部分可以为空的
8? Wxd65) [font="Times]class ForVar {
]fo^43rn{ [font="Times]public static void main(String args[]) {
8G&+ [font="Times]int i;
3]n@c?lw [font="Times]boolean done = false;
_`i%9Ad.4 [font="Times]i = 0;
zI_GdQNfN [font="Times]for( ; !done; ) {
@jSbMI [font="Times]System.out.println("i is " + i);
s}9tK(4v [font="Times]if(i == 10) done = true;
dqA[|bV [font="Times]i++;
~h0BT(p/ [font="Times]}
([b!$o<v [font="Times]}
y*h1W4:^- [font="Times]}
循环语句的例子下载 #Jz&9I<OKx [font="Times] 2.分支语句[font="Times]
86fK=G:> [font="Times] if/else语句
c[_^bs>k [font="Times]class IfElse {
L8wcH [font="Times]public static void main(String args[]) {
@[tV_Z%,b [font="Times]int month = 4; // April
8sIA;r%S [font="Times]String season;
AAq=,=:R< [font="Times]if(month == 12 || month == 1 || month == 2)
F(9
Y/UXH [font="Times]season = "Winter";
.*-w UBr [font="Times]else if(month == 3 || month == 4 || month == 5)
B36puz 0{ [font="Times]season = "Spring";
OP`Jc$|6 [font="Times]else if(month == 6 || month == 7 || month == 8)
?%/u/*9rj [font="Times]season = "Summer";
X2dc\v.x [font="Times]else if(month == 9 || month == 10 || month == 11)
^y0C5Bl; [font="Times]season = "Autumn";
[Cj)@OC [font="Times]else
?7MwTi8{F [font="Times]season = "Bogus Month";
tQ/
#t<4D [font="Times]System.out.println("April is in the " + season + ".");
HJaw\zbL [font="Times]}
kEhm' [font="Times]}
ct4 [b| [font="Times]//这段程序输出[font="Times]:
E? eWv)// [font="Times]//April is in the Spring.
}?]yxa ~ [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
[~c'|E8Q [font="Times] switch语句
<o!&Kk 9 [font="Times] class Switch {
_b_?9b-)D [font="Times]public static void main(String args[]) {
``|RO[+2 [font="Times]int month = 4;
dMs||&|& [font="Times]String season;
{{*]bGko [font="Times]switch (month) {
AXP`,H [font="Times]case 12:
7X{bB [font="Times]case 1:
bLEATT[ [font="Times]case 2:
1i /::4= [font="Times]season = "Winter";
nt0\q'& [font="Times]break;
)R8%'X;U [font="Times]case 3:
#3K,V8( [font="Times]case 4:
[AZaT [font="Times]case 5:
q@!'R{fu [font="Times]season = "Spring";
"WbVCT'i [font="Times]break;
g(1B W#$ [font="Times]case 6:
gFs/012{ [font="Times]case 7:
@>fO;* [font="Times]case 8:
sCtw30BL [font="Times]season = "Summer";
7ec0Xh1 [font="Times]break;
p/k<wCm6 [font="Times]case 9:
poQdI?ed, [font="Times]case 10:
F|?+>c1} [font="Times]case 11:
9#&W!f*qO| [font="Times]season = "Autumn";
l^ 0_>R [font="Times]break;
hzQ+9-qA [font="Times]default:
/}$T38 [font="Times]season = "Bogus Month";
:Wg-@d [font="Times]}
(#bp`Kih [font="Times]System.out.println("April is in the " + season + ".");
xd|~+4 [font="Times]}
!ASoXQRz [font="Times]}
分支语句代码下载 TD{=L*{+ ;EJPrDHTk [font="Times]switch语句适合于条件非常多的逻辑
inPE/Ux 请看上述语句可以混合使用,请看
下载例子